The present invention relates to a method and a device for coating a body rotating about an axis, whereby a relative movement takes place in the direction of the axis of rotation between the body and a nozzle which ejects a reaction mixture forming a polyurethane, so that application is effected in helical convolutions.
The coating of rotating bodies according to this method is generally known. The method can be used for the production of hollow bodies, in particular of pipes, by the coating of a removable core or mandrel. Difficulties arise depending on parameters such as circumferential speed and rate of feed of the body or the nozzle. In particular there is a risk of air blisters and inadequate contact of individual convolutions. Hence attempts have already been made in the production of pipes by the coating of a core to apply the reaction mixture to a carrier tape and to wind the latter about a core, whereby the gap that is present between the individual convolutions is filled up with reaction mixture (see, e.g., European Patent 523,509). Due to this additional filling of the gap, the expenditure on process technology and machinery is considerable. In addition, this method is not suitable for the coating of bodies, since it is not possible to dispense with the carrier tape.
The object of the present invention was to improve the method in such a way that flawless coatings can be produced economically.